trail - evidence pointing to a possible solution; the police are following a promising lead; the trail led straight to the perpetrator track, lead evidence, grounds - your basis for belief or disbelief; knowledge on which to base belief; the evidence that smoking causes lung cancer is very compelling
The process by which the oceanic crust is pulled under the continental crust is called subduction and the zone at which this occurs at the plate boundaries is called the subduction zone. At the subduction zone where the oceanic crust sinks beneath the continental crust a deep oceanic trench or valley is created.
As the oceanic plate is subducted sediment is scraped off to form an acretionary wedge at the point of collision between the two plates. When the oceanic plate is subducted due to partial melting of the asthenosphere magma with an andesitic composition is formed.